France will boost its military presence in the troubled Sahel region of Africa where jihadist groups operate to support the fight against Boko Haram, Defence Minister Jean-Yves Le Drian said Wednesday.

France said on Sunday its military offensive that freed northern Mali from the grip of Islamists would be replaced by an operation spanning the wider, largely lawless Sahel region to combat extremist violence.

The UN chief told the Security Council yesterday that the crisis in Mali, where Islamist groups allied with al Qaeda now control the north, is part of "a sustained, systemic crisis across the entire Sahel region."